Allergic diseases account for more than 500,000 hospitalizations and 5,000 deaths per year in the U.S. with allergic rhinitis affecting another 20 million individuals. Allergic patients produce enhanced levels of IgE, which binds to high affinity receptors (FceRI) expressed on basophils and mast cells. Allergen exposure results in the aggregation of receptor-bound IgE triggering release of mediators that induce allergic responses. Chemotactic factors, especially IL-5, are also produced along with factors that enhance vascular permeability resulting in the late phase allergic response. Therapeutics that block the effects of FceRI and IL-5 receptor signaling will have a profound effect on these disease processes. The goal of Phase I is to design high-throughput screening (HTS) assays to discover pharmacological agents that target intracellular signal transduction events known to be essential for FceRI and IL-5 receptor function. The investigators plan to generate a recombinant GST- fusion protein containing the proline-rich region of the p85 subunit of PI-3 kinase fused to a b-galactosidase reporter. This fusion protein will be used to establish a functional binding assay with the Lyn SH3 domain in a 96- well format in preparation for Phase II HTS of diverse synthetic, combinatorial and natural product libraries to identify specific antagonists of this interaction.